This invention relates to communication systems and, in particular, to communication systems which utilize aggregating networks to couple traffic from traffic sources to destinations.
In modern communication systems, the transfer of traffic from a traffic source to a destination often involves passage of the traffic through various types of aggregating networks. In a typical communication system, the aggregating networks are formed by switching systems which include aggregating elements such as multiplexors, concentrators and/or digital switches.
An aggregating network is shared by the traffic from many traffic sources. Accordingly, before an aggregating network can act on a connection request of a traffic source, a connection acceptance/rejection decision must be made. If the connection acceptance/rejection decision is to accept a connection request, the traffic from the requesting traffic source is coupled by the aggregating network to the outgoing link associated with the connection request. If the connection acceptance/rejection decision is to reject the connection request, the aggregating network is inhibited so that no coupling of traffic occurs.
In present communication systems, in order to safeguard against the loss of information, the connection acceptance/rejection decisions are made based on maintaining the sustainable rate, i.e., the mean or average rate, of traffic on an outgoing link at or below a preselected percentage, e.g., 50%, of the maximum link rate. Thus, if the additional traffic from a traffic source would result in a sustainable rate of traffic which exceeds the preselected percentage of the maximum link rate, the connection request is rejected. On the other hand, if the additional traffic would result in a sustainable rate which is less than the preselected percentage of the maximum link rate, the connection request is accepted.
The use of the aforesaid criteria, i.e., maintaining the traffic on an outgoing link at or below a preselected percentage of the maximum link rate, indirectly attempts to account for the so-called "burstiness" of the traffic on a link. Burstiness refers to the variance of or changes in the arrival rate of traffic arriving on a link. By providing a wide margin between the actual sustainable rate and the maximum link rate, there is a good likelihood that any burstiness or variance from the sustainable rate will not cause the maximum link rate to be exceeded. However, by not directly accounting for the burstiness of traffic on a link, the link is still susceptible to loss of information due to bursts of traffic. Moreover, by operating a link well below its maximum link rate, link capacity is wasted and operating efficiency is lessened.
It is, therefore, an object of the present invention, to provide a communication system with an improved ability to make connection acceptance/rejection decisions.
It is a further object of the present invention to provide a communication system in which connection acceptance/rejection decisions are made in a manner which efficiently utilizes the outgoing telephone links of the system.
It is a further object of the present invention to provide a communication system in which connection acceptance/rejection decisions are made in a relatively simple and easy manner.
It is yet a further object of the present invention to provide a communication system in which connection acceptance/rejection decisions take direct account of the burstiness of traffic on a link.